Electrical conducting structure and liquid crystal display device comprising the same

ABSTRACT

An electrical conducting structure including an integrated circuit, a substrate, and a plurality of bumps, wherein at least one bump comprises a first conductive part connected to the integrated circuit at one end; a second conductive part connected to the integrated circuit at one end; a conductive connection part connecting the first conductive part and the second conductive part; a first insulation part surrounding the first conductive part and the second conductive part; and a second insulation part located between the first conductive part and the second conductive part.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a conducting structure, and more particularly,to a conducting structure with flexibility.

2. Description of the Prior Art

In the fabrication of liquid crystal displays, some of the modulepackage techniques common used today includes tape automated bonding(TAB), chip on glass (COG), and chip on film (COF). In TAB, numerousbumps are utilized for connecting a polyimide board and a liquid crystaldisplay panel via an anisotropic conductive film (ACF) after the drivingchip is fabricated. The bumps are essentially metal blocks comprisinggold or lead-tin alloy on the bonding pad of the chip and duringfabrication, the bumps are melted to connect the bonding pad and thecircuits together. In COG, driving chips with fabricated bumps areconnected directly onto an LCD panel by an anisotropic conductive filmvia a flip chip package. In COF, the electrical circuit originallydesigned for the printed circuit board is positioned on the polyimideboard together with the driving chip.

In the past, TAB has generally been utilized for fabricating larger LCDpanels whereas COG has been used for fabricating medium to small sizeLCD panels. However in recent years, COG has been widely used forfabricating LCD panels of various sizes in order to reduce cost of thepanels. Nevertheless, numerous problems that ultimately affectproduction yield and quality of display still remain when the existingCOG technique is applied to LCD panel fabrication.

Please refer to FIG. 1. FIG. 1 is a schematic view of the COG techniqueaccording to the prior art. By fabricating bumps 106 on the pad of anintegrated circuit 102 and utilizing an anisotropic conductive film 108as the interface, the integrated circuit 102 can be smoothly connectedonto an LCD panel 104. In general, the bumps 106 are composed ofmaterials such as gold or lead-tin alloy and the anisotropic conductivefilm 108 is composed of materials including numerous conductive pellets.By melting the conductive pellets between the bumps 106 and theanisotropic conductive film 108 via a hot embossing fabrication, theintegrated circuit 102 can be electrically connected to a connection padon the LCD panel 104. A high temperature (160to 190°C.) is normallyrequired to carry out the hot embossing fabrication, and because of thefact that the heat expansion coefficient between the integrated circuit102 and the LCD panel 104 differs significantly, an enormous amount ofstress is often generated at the contact surface when the temperaturereturns to normal. As shown in FIG. 2, the resulting stress often causesa bending phenomenon on the integrated circuit 102 and the LCD panel104. Eventually, the phenomenon would further induce a curtain mura anddegrade the overall quality of the display.

In the prior art COG technique, the smoothness of the LCD panel 104becomes particularly important as the integrated circuit 102 and the LCDpanel 104 are composed of hard and rigid materials. In general, thesmoothness of the LCD panels must be controlled to within a range of±0.5 μm and the smoothness requirements for larger LCD panels are evenstricter. Essentially, an LCD panel with poor smoothness often resultsin a connection failure between the integrated circuit 102 and the LCDpanel 104 and ultimately decreases the overall product yield.

Moreover, since the anisotropic conductive film that includes numerousconductive pellets is commonly used for connecting the integratedcircuit 102 and the LCD panel 104, maintaining a safe distance betweenthe bumps 106 therefore becomes a critically important matter forpreventing a short circuit. Please refer to FIG. 3. FIG. 3 is aschematic view of the connection between the bump 106, conductivepellets 108 a, and the integrated circuit 102 and LCD panel 104. If thedistance between the bumps 106 is too short and the conductive pellets108 a are concentrated in one area, a short circuit will be occurredbetween the bumps 106 and it will decrease the product yield. Accordingto the prior art about COG technique, a distance of more than 15 μmbetween the bumps 106 is generally required in order to control theprobability of a short circuit to be within an acceptable range. As aresult, the contact area between the integrated circuit and the LCDpanel needs to be maintained above a certain size and it is anunavoidable challenge to reducing the size of the contact area.

SUMMARY OF INVENTION

It is therefore an objective of the present invention to provide aconductive structure with flexible bumps for effectively preventing thebending phenomenon between the integrated circuit and the LCD panel andproblems such as curtain mura.

In addition, a second objective of the present invention is to provide aconductive structure with flexible bumps for increasing the tolerancelevel of Chip On Glass (COG) technique to the smoothness of the glasssubstrate.

The third objective of the present invention is to provide a conductivestructure with bumps surrounded by an insulating layer for preventingshort circuits and for reducing the contact area between the integratedcircuit and the LCD panel.

According to the present invention, a conductive structure includes anintegrated circuit, a substrate, and a plurality of bumps locatedbetween the integrated circuit and the substrate. At least one bumpcomprises a first conductive part connected to the integrated circuit atone end; a second conductive part connected to the integrated circuit atone end; a conductive connection part connecting the first conductivepart and the second conductive part; a first insulation part surroundingthe first conductive part and the second conductive part; and a secondinsulation part locating between the first conductive part and thesecond conductive part.

According to the present invention, a liquid crystal display comprises asubstrate, a liquid crystal display region positioned in the center ofthe substrate, an integrated circuit positioned on the edge of thesubstrate, a plurality of bumps positioned between the substrate and theintegrated circuit for electrically connecting the integrated circuit,and an anisotropic conductive film for providing an electricalconnection between the bumps and the substrate. At least one bumpcomprises a first conductive part connected to the integrated circuit atone end; a second conductive part connected to the integrated circuit atone end; a conductive connection part connecting the first conductivepart and the second conductive part; a first insulation part surroundingthe first conductive part and the second conductive part; and a secondinsulation part locating between the first conductive part and thesecond conductive part.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of the COG technique according to the priorart.

FIG. 2 is a schematic view of the bending phenomenon caused by the COGtechnique according to the prior art.

FIG. 3 is a schematic view of a short circuit condition caused by theCOG technique according to the prior art.

FIG. 4 is a schematic view of the means by which the bumps of theconductive structure are connected to the integrated circuit accordingto the present invention.

FIG. 5 is a schematic view of the means by which the bumps of theconductive structure are connected to the integrated circuit accordingto the present invention.

FIG. 6 is a schematic view of the conductive structure in which thebumps are connected to the integrated circuit and the glass substrateaccording to the present invention.

FIG. 7 is a schematic view of the conductive structure in which thebumps are connected to an uneven surface according to the presentinvention.

FIG. 8 is a schematic view of the conductive structure in which thedistance between bumps is reduced according to the present invention.

FIGS. 9, 10, and 11 show schematic upward views of the bumps of theconductive structure according to the present invention.

FIGS. 12 and 13 show another embodiment of the bumps of the conductivestructure according to the present invention.

FIGS. 14 and 15 show another embodiment of the bumps of the conductivestructure according to the present invention.

FIGS. 16 and 17 show another embodiment of the bumps of the conductivestructure according to the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 4 and FIG. 5. FIG. 4 and FIG. 5 are schematic viewsof the means by which the bumps of the conductive structure areconnected to the integrated circuit according to the present invention.The bumps in FIG. 4 and FIG. 5 comprise a first conducting part 2041, asecond conducting part 2042, a conductive connection part 208, and aninsulation layer 206. The insulation layer 206 can be further dividedinto a first insulation part 2101 and a second insulation part 2102based on its location of formation. One end of the first conductive part2041 and one end of the second conductive part 2042 are connected to theintegrated circuit 202, and the other ends of the two conductive partsare connected to the conductive connection part 208. The firstconductive part 2041 and the second conductive part 2042 are surroundedby the first insulation part 2101. The second insulation part 2102 islocated between the first conductive part 2041 and the second conductivepart 2042.

During the fabrication of the conductive structure bumps, the insulationlayer 206 is first formed on a contact of the integrated circuit 202 andtwo openings are formed on the insulation layer 206 to expose thecontact of the integrated circuit 202. Then a first conductive part 2041and a second conductive part 2042 are formed in the two openings.Thereafter, a conductive connection part 208 is formed on the firstconductive part 2041 and the second conductive part 2042. The conductiveconnection part 208 is electrically connected to the integrated circuit202 through the first conductive part 2041 and the second conductivepart 2042. The insulation layer 206 is divided into the first insulationpart 2101 and the second insulation part 2102. The first insulation part2101 surrounds the first conductive part 2041 and the second conductivepart 2042, whereas the second insulation part 2102 is located betweenthe first conductive part 2041 and the second conductive part 2042. Theinsulation layer 206 comprises light-isolating materials such aspolyimide (PI), a strong isolating material with flexibility. In orderto form the first conductive part 2041 and the second conductive part2042, an electroless fabrication method can be employed to form gold,nickel, gold alloy, or nickel alloy in the openings, and ultimately toelectrically connect to the contact of the integrated circuit 202. Inaddition, the composition of the conductive connection part 208 isselected from materials such as gold or gold alloys.

In the preferred embodiment of the present invention, when the height ofthe first conductive part 2041 and the second conductive part 2042 isH1, the height of the conductive connection part 208 is H2, and theheight of the first insulation part 2101 is H3, the relationship amongthe three heights becomes H1≦H3<H1+H2. The condition where H1=H3 isshown in FIG. 4, while the condition where H3=H1+H2 is shown in FIG. 5.

Please refer to FIG. 6. FIG. 6 is a schematic view of the conductivestructure in which the bumps are connected to the integrated circuit andthe glass substrate according to the present invention. In order toestablish a connection between the integrated circuit 202 and the glasssubstrate 212, the integrated circuit 202 needs to be electricallyconnected to a contact pad on top of the glass substrate 212 via hotembossing fabrication by melting the conductive connection part 208 andthe conductive pellets 210. After the integrated circuit 202 and theglass substrate 212 return to room temperature, the stress remaining inthe contact surface is removed by a deformation of the bumps due totheir flexible nature. As shown in FIG. 6, the bump is deformed into atrapezoid structure to remove the stress remaining in the horizontaldirection. Consequently, the bending phenomenon of the integratedcircuit 202 and the glass substrate 212 is greatly reduced and problemssuch as curtain mura can also be prevented.

Please refer to FIG. 7. FIG. 7 is a schematic view of the conductivestructure in which the bumps are connected to an uneven surfaceaccording to the present invention. The condition shown in FIG. 7 duringthe compression process is often caused by an uneven surface on theintegrated circuit 202 and/or the glass substrate 212. Due to thecompressible nature of the bumps and the fact that the insulation layer206 is composed of a flexible material, the bumps are able to conformwith the compression surface to a certain extent. By utilizing the bumpsof the present invention, a greater tolerance level to the smoothness ofthe LCD panel is achieved and thus, the overall fabrication yield isincreased.

Please refer to FIG. 8. FIG. 8 is a schematic view of the conductivestructure in which the distance between bumps is reduced according tothe present invention. Even when the distance between the bumps isreduced and the conductive pellets 210 are concentrated between twobumps, the bumps are still electrically insulated from each other due tothe design of the insulation layer 206. As a result, the area of thecontact region and the distance between the integrated circuit 202 andthe glass substrate 21 2 can be greatly reduced. As shown in FIG. 8, theinsulation layer 206 only separates the contact between the firstconductive part 2041 and the second conductive part 2042 but not theneighboring conductive connection part 208. In another preferredembodiment, the insulation layer 206 can be extended downward to furtherprotect the conductive connection part 208, as shown in FIG. 5.

Please refer to FIG. 9. FIG. 9 is a schematic upward view of the bumpsof the conductive structure according to the present invention. As shownin FIG. 9, the upward view of both the first conductive part 2041 andthe second conductive part 2042 is rectangular. The shape of these twoconductive parts can also be square, as shown in FIG. 10 or circular, asshown in FIG. 11. Essentially, a bump should include at least oneconductive part, such as the two conductive parts 2041 and 2042 as shownin FIG. 9, or a plurality of conductive parts 2041 and 2042, as shown inFIG. 10 and FIG. 11. As long as the conductive connection part 208 iselectrically connected to the contact of the integrated circuit 202, thefirst conductive part 2041 and the second conductive part 2042 can betriangular, tetragonal, polygonal, cylindrical, or elliptical.

Please refer to FIGS. 12 and 13. FIG. 12 and FIG. 13 show anotherembodiment of the bumps of the conductive structure according to thepresent invention. As shown in FIG. 12, the first conductive part 2041and the second conductive part 2042 are a monolithically-formedstructure. The structure has a hollow region in the center. The secondinsulation part 2102 is located within the hollow region, and the firstconductive part 2041 and the second conductive part 2042 are surroundedby the first insulation part 2101. As shown in FIG. 13, a plurality ofthe first conductive part 2041 and the second conductive part 2042comprising the hollow region in the center are utilized for forming thebumps of the present invention. In FIG. 13, the second insulation part2102 is also located within the hollow region and the first conductivepart 2041 and the second conductive part 2042 are surrounded by thefirst insulation part 2101.

Please refer to FIG. 14 and FIG. 15. FIG. 14 and FIG. 15 show anotherembodiment of the bumps of the conductive structure according to thepresent invention. As shown in FIG. 14, the first conductive part 2041and the second conductive part 2042 are a monolithically-formedstructure. The structure has a square hollow region in the center. Thesecond insulation part 2102 is located within the hollow region, and thefirst conductive part 2041 and the second conductive part 2042 aresurrounded by the first insulation part 2101. As shown in FIG. 15, aplurality of the first conductive part 2041 and the second conductivepart 2042 comprising the square hollow region are utilized for formingthe bumps of the present invention. In FIG. 15, the second insulationpart 2102 is also located within the square hollow region and the firstconductive part 2041 and the second conductive part 2042 are surroundedby the first insulation part 2101. In this embodiment, the firstconductive part 2041 and the second conductive part 2042 neighboring toeach other can be interconnected to form an even stronger structure.

Please refer to FIG. 16 and FIG. 17. FIG. 16 and FIG. 17 show anotherembodiment of the bumps of the conductive structure according to thepresent invention. This embodiment is essentially a variation derivedfrom the embodiment shown in FIG. 12 and FIG. 13. As shown in FIG. 16,the first conductive part 2041 and the second conductive part 2042 are amonolithically-formed structure. The first conductive part 2041 and thesecond conductive part 2042 also form a hollow post that includes anopening. The external first insulation part 2101 and the internal secondinsulation part 2102 form a monolithically-formed structure thateventually becomes the insulation layer 206. As shown in FIG. 17, aplurality of the first conductive part 2041 and the second conductivepart 2042 comprising the hollow post are utilized for forming the bumpsof the present invention.

Since the integrated circuit 202 and the glass substrate 212 arecomposed of hard and rigid materials, a modified conductive bump can befurther utilized according to the present invention to increase thetolerance level of the COG technique to the smoothness of the glasssubstrate. The modified conductive bump includes a buffer layer that iscapable of undergoing deformation during a connection. The buffer layerdeformation is able to compensate for connection problems caused byuneven contact between the bumps and the glass substrate and the heightof the bumps, and consequently increases fabrication variability andproduction yield. In addition, a multi-layered metal layer is formed ontop of the buffer layer. The multi-layered metal layer is composed of anadhesion layer, a shielding layer, and a protective layer and theconductive bump is positioned on top of the metal layer. Characterizedby having a buffer layer with low Young's modulus, the conductive bumpensures a much tighter connection during an affixing process and alsoprevents having uneven electrical resistance at the point of contact.

In contrast to the prior art, the present invention introduces theconductive structure to provide distinguishing features includingbendable and compressible bumps that are insulated from each otherhorizontally, thereby effectively reducing the production cost, reducingthe final product size, and increasing the product yield.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A conductive structure comprising: an integrated circuit; asubstrate; and a plurality of bumps positioned in between the integratedcircuit and the substrate wherein at least one of the bumps comprises: afirst conductive part connected to the integrated circuit at one end; asecond conductive part connected to the integrated circuit at one end; aconductive connection part connecting the first conductive part and thesecond conductive part; a first insulation part surrounding the firstconductive part and the second conductive part, wherein the height ofthe first conductive part and the second conductive part is H1, theheight of the conductive connection part is H2, the height of the firstinsulation part is H3, and H1≦H3≦H1+H2; and a second insulation partpositioned in between the first conductive part and the secondconductive part.
 2. The conductive structure of claim 1 wherein ananisotropic conductive film (ACF) is positioned in between theintegrated circuit and the substrate for providing an electricalconnection between the conductive connection part and the substrate. 3.The conductive structure of claim 1 wherein the first conductive partand the second conductive part comprise gold, nickel, gold alloy, ornickel alloy.
 4. The conductive structure of claim 1 wherein theconductive connection part comprises gold or gold alloy.
 5. Theconductive structure of claim 1 wherein the first insulation part andthe second insulation part comprise light-isolating materials.
 6. Theconductive structure of claim 5 wherein the light-isolating material ofthe first insulation part and the second insulation part is polyimide.7. The conductive structure of claim 1 wherein the first insulation partand the second insulation part are a monolithically-formed structure. 8.The conductive structure of claim 1 wherein the first conductive partincludes a first hollow section.
 9. The conductive structure of claim 1wherein the second conductive part includes a second hollow section. 10.The conductive structure of claim 1 wherein the first conductive part isa post.
 11. The conductive structure of claim 10 wherein the post is atriangular post, a tetragonal post, a polygonal post a cylindrical post,or an elliptical post.
 12. The conductive structure of claim 1 whereinthe second conductive part is a post.
 13. The conductive structure ofclaim 12 wherein the post is a triangular post, a tetragonal post, apolygonal post, a cylindrical post, or an elliptical post.
 14. Theconductive structure of claim 1 wherein the first conductive part andthe second conductive part are a monolithically-forned post.
 15. Theconductive structure of claim 14 wherein the post is a hollow post. 16.The conductive structure of claim 15 wherein the second insulation partis located inside the hollow post.
 17. The conductive structure of claim16 wherein the hollow post includes an opening.
 18. The conductivestructure of claim 17 wherein the first insulation part and the secondinsulation part are a monolithically-formed structure.
 19. A liquidcrystal display comprising: a substrate; a liquid crystal display regionpositioned in the center of the substrate; an integrated circuitpositioned on the edge of the substrate; a plurality of bumps positionedin between the substrate and the integrated circuit for electricallyconnecting the integrated circuit; and an anisotropic conductive filmfor providing an electrical connection between the bumps and thesubstrate, wherein the plurality of bumps further comprises: a firstconductive part connected to the integrated circuit at one end; a secondconductive part connected to the integrated circuit at one end; aconductive connection part connecting the first conductive part and thesecond conductive part; a first insulation part surrounding the firstconductive part and the second conductive part, wherein the height ofthe first conductive part and the second conductive part is H1 theheight of the conductive connection part is H2. the height of the firstinsulation part is H3, and H1≦H3≦H1+H2; and a second insulation partpositioned in between the first conductive part and the secondconductive part.
 20. The liquid crystal display of claim 19 wherein thefirst conductive part and the second conductive part comprises gold,nickel, gold alloy, or nickel alloy.
 21. The liquid crystal display ofclaim 19 wherein the conductive connection part comprises gold or goldalloy.
 22. The liquid crystal display of claim 19 wherein the firstinsulation part and the second insulation part comprise light-isolatingmaterials.
 23. The liquid crystal display of claim 19 wherein thelight-isolating material of the first insulation part and the secondinsulation part is polyimide.
 24. The liquid crystal display of claim 19wherein the first insulation part and the second insulation part are amonolithically-formed structure.
 25. The liquid crystal display of claim19 wherein the first conductive part includes a first hollow section.26. The liquid crystal display of claim 19 wherein the second conductivepart includes a second hollow section.
 27. The liquid crystal display ofclaim 19 wherein the first conductive part is a post.
 28. The liquidcrystal display of claim 27 wherein the post is a triangular post, atetragonal post, a polygonal post, a cylindrical post, or an ellipticalpost.
 29. The liquid crystal display of claim 28 wherein the secondconductive part is a post.
 30. The liquid crystal display of claim 29wherein the post is a triangular post, a tetragonal post, a polygonalpost, a cylindrical post, or an elliptical post.
 31. The liquid crystaldisplay of claim 19 wherein the first conductive part and the secondconductive part are a monolithically-formed post.
 32. The liquid crystaldisplay of claim 31 wherein the post is a hollow post.
 33. The liquidcrystal display of claim 32 wherein the second insulation part islocated inside the hollow post
 34. The liquid crystal display of claim33 wherein the hollow post includes an opening.
 35. The liquid crystaldisplay of claim 34 wherein the first insulation part and the secondinsulation part are monolithically-formed structure.